<div id="outerdiv" style="position:fixed;top:0;left:0;background:rgba(0,0,0,0.4);z-index:2;width:100%;height:100%;display:none;">
    <div id="innerdiv" style="position:absolute;">
        <img id="bigimg" style="border:3px solid #fff;border-radius: 3px" src="" />
    </div>
</div>